Considering that I thought Doom 3 was a bit tiresome, especially right before Hell, ROE was a total trudge for me. I didn't like the double-barrel, or the bosses. The worst part was the inclusion of the Vulgars: they were totally overused, and were basically just a slightly more powerful Imp, which became highly irritating after a short time. Best part was, as Face23785 mentioned, the Delta Labs level. Think I godmode'd through most of the second half of the game, though, just to be done with it.

I've beaten ROE and not Doom 3, so my opinion is a bit biased, but I kinda liked ROE better. It had the super shotty, old school lost souls, that gravity gun rip-off, the weird bleedy heart power-up, and some pretty epic Hell segments. I had a lot of fun with it.

The lighting isn't as tastefully done in RoE. Whereas in DOOM 3, I had plenty of moments of awe-inspiring splendor and had to stop and take screenshots, RoE had too many moments where it felt like the GoldenEye 007 (n64) team had come and just splattered their terrible colored lighting sensibilities all over the maps.

That said, the gameplay is arguably better and more in-depth in RoE, though you can easily abuse it as you get exponentially more powerful. It is also quite a bit shorter than DOOM 3. Worth playing though, for sure.

Lighting in Doom 3 is a bitch to work with. Stuff either looks awesome or shitty depending on precise adjustments to things and certain light texture/object texture combinations. It's possible to get the lighting in Doom 3 maps looking so good that they visually compete with more modern games, but only after a lot of time and work. I don't think Nerve did too bad of a job though.

I think Doom 3 RoE is a completion to simple Doom 3. The Super Shotgun and the few extra monsters don't hurt the gameplay. Still, they're not as important as the Doom 2 monsters in classic Doom. I'd say it's better with the RoE monsters, because fighting only Imps gets old. Fighting both Imps and Vulgars helps reduce this monotony. Also, the Bruisers are quite good surprise hitters, and there's no equivalent in simple Doom 3 for them. So I'd say that RoE wins, but I'm not very fond of anything else about it.

Tetzlaff said:
You make it sound as if Imps were the only monsters available in Doom3...

No, but they were fairly common (kind of like the Ogres in Quake) and their screams made them obnoxious, and eventually became almost as easy as classic Doom Imps (still slightly harder, because of hit points and how violent they are).

Just finished RoE, so my impressions are fresh like prince of Bel-Air. First of all, new monsters are simply unoriginal and bland. More powerful version of the Imp is the worst idea ever.

The levels are okay, but encounter design is very bad. For example in the room with a power plant, that giant plasma beam in the middle of a room, those new lost souls fly out, one by one, from the top of the beam, and you just stand in one place and casually snipe them with MG. G-sec guys probably received lobotomy from Nerve, because they almost always acted extremely scripted and stupid. Spam of Revenants in the late game also wasn't cool, made me wish i was in Hell (already).

Grappling gun is a cheap and lame gimmick, both in HL2 and RoE. Someday I'll write a whole article on this subject.

Artifact is overpowered and developers throw an unrealistic traps at you right after you get the slow-mo.

First boss is cool, the second one is too easy (hmmm, giant red heart in the chest of a boss, i wonder where should i shoot, oh, thanks camera close up), same for the third. But that's because, you know, Artifact is too powerful.

I found the artifact to actually be rather well done, or at least it worked well for most of the encounters. Even though, many of the encounters were kind of lame. The gravity gun thought was very stupid and almost completely useless except for the first boss.